1. Field of the Invention
The present invention relates to an exposure device for exposing an imaging region and forming an image at a recording medium, such as a printed circuit board or the like, with a laser beam which is modulated in accordance with image data.
2. Description of the Related Art
Devices disclosed in, for example, Japanese Patent Application Laid-Open (JP-A) No. 2000-275863 are known as laser exposure devices for forming wiring patterns of printed circuit boards and the like.
In a scanning imaging device described in JP-A No. 2000-275863, positioning holes (alignment marks) are provided respectively at four corners of a printed circuit board, which is placed on a table for conveyance of the board. The positioning holes are moved along a sub-scanning direction with the table from a standby position to a position of measurement by a CCD camera. This CCD camera image-captures each of the positioning holes of the printed circuit board. Hence, processing for alignment of image data is executed after shifting (converting co-ordinates of) an imaging object region through imaging co-ordinates such that the imaging object region corresponds to a position of the printed circuit board as obtained by the image capture. Thereafter, the table is returned to the standby position. Then, while the table is being moved in the sub-scanning direction at a predetermined image formation speed, a latent image corresponding to a wiring pattern is formed at a predetermined region (the imaging region) of the printed circuit board by scanning and exposing the printed circuit board with a laser beam. The laser beam is modulated at exposure positions of the laser beam on the basis of the image data and deflected in a main scanning direction by a polygon mirror.
In the laser exposure device as disclosed in JP-A No. 2000-275863, in a case in which image formation is to be carried out at a single imaging region of the printed circuit board, exposure of the imaging region of the printed circuit board cannot commence until the printed circuit board has moved from the standby position to the position of measurement of the alignment marks, the positions of the alignment marks of the printed circuit board have been measured, and then the printed circuit board has returned to the standby position.
Further, in order to improve productivity and imaging accuracy at a printed circuit board, there is a method of providing a plurality of imaging regions at which respectively independent wiring patterns are formed and a plurality of alignment marks which are in respective correspondence with these imaging regions, in a print circuit board.
If respective wiring patterns are formed at a plurality of imaging regions of a printed circuit board by the laser exposure device described in JP-A No. 2000-275863, when exposure of one of the imaging regions finishes, exposure of the next imaging region of the printed circuit board cannot be commenced until after the printed circuit board has temporarily returned from an exposure position to a standby position, and position measurement of the corresponding set of alignment marks after has been completed.
In consequence, in such a laser exposure device, as the number of imaging regions provided at a printed circuit board increases, the amount of time required for position measurement of the alignment marks increases, and an image-forming time for the whole of one printed circuit board increases remarkably.